Proceedings of the Iowa Academy of Science
Volume 33 Annual Issue Article 39
1926
Some Recent Finds of Remains of the Extinct Ground Sloth in Southwest Iowa
Fred Delavan State University of Iowa
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Recommended Citation Delavan, Fred (1926) "Some Recent Finds of Remains of the Extinct Ground Sloth in Southwest Iowa," Proceedings of the Iowa Academy of Science, 33(1), 203-205. Available at: https://scholarworks.uni.edu/pias/vol33/iss1/39
This Research is brought to you for free and open access by the Iowa Academy of Science at UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academy of Science by an authorized editor of UNI ScholarWorks. For more information, please contact [email protected]. Delavan: Some Recent Finds of Remains of the Extinct Ground Sloth in South
scnrn RECENT FINDS OF RE~fAINS OF THE EX TINCT GROUND SLOTH IN SOUTffWEST IOWA
FRED DELAVAN Evidence of the extinct ground sloth in Iowa is very meager, but additional remains are being brought forth yearly. At the present time the knowledge of its presence is limited almost en tirely to the counties bordering the Missouri River; the one ex ception is Dubuque County, in the middle eastern portion of the state. Three specimens have been added to the collection in the past year. A tooth of the Megalonyx from Dixon Creek, Fremont County, collected by George Day, and a tooth and claw bone from Chabaneau Creek, Mills County, collected by the writer. The tooth from Chabaneau is exceptionally long and well preserved. For the benefit of those who have not made a study of the ground sloth, I will give a brief history. The sloths are divided into two main groups, the Tardigrada, or tree-sloth, and the Grav igrada, or extinct ground-sloth. The Gravigrada are the only sloths which are known to have existed in Iowa, and two genera of these have been found; Megalonyx and Mylodon. Of these two, Megalonyx seems to be the more common. The chief difference between Megalonyx and ~Jylodon is that the bones of Mylodon are shorter and heavier proportionally than those of Megalonyx; its head is flat while that of Megalonyx has a sharply defined ridge running down to the base of the skull. The cla\v differs in that it has a slight inward curvature, and the tooth in that it has a triang ular pattern in Megalonyx, and is round in Mylodon. The ground-sloth was of gigantic size; some specimens measur ing eleven feet long, and nearly five feet high - compared to the modern tree-sloth, which is only about two feet long. The habits of the ground-sloth were similar to those of the modern tree-sloth, in that it lived on vegetation. Unlike its smaller relative it was unable to climb among· the branches, due to its great size, but, as stated by Professor Owen, the enormously strong bones of these animals indicate that they could uproot trees of considerable size in order to get the foliage. As to the length of time since the ground-sloth has disappeared, investigations of sloth finds in South America have revealed bones
Published by UNI ScholarWorks, 1926 203 1 Proceedings of the Iowa Academy of Science, Vol. 33 [1926], No. 1, Art. 39 204 IOWA ACADEMY OF SCIENCE
and pieces of hide to which tendons and fibres of muscle are still attached; indicating that they have lived there at least in the recent past. A find in Patagonia; Chile, revealed the remains of sloths associated with evidences of human occupation, among which were some remains of cut hay. The conclusion was reached that at some time past, men kept these great creatures in captivity for some purpose. The sloth has a very simple type of teeth, consisting of five molars above and four below; tooth formula : i ~ c £ m ~4 • They are of columnar structure, and have no roots. They are without
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,...... ,...... _ _, J\jO D 114 enamel, but have a hard outer covering. There are no ridges on the face of the tooth, but the pulp in the center wears down more rapidly than the outer edge, so that it makes some semblence of a cutting edge. , The tooth has a persistent pulp, so that as it wears down it grows out, thus maintaining the normal length. The claws of the sloth were exceptionally long and powerful; and were protected by a sheath of bone which extended entirely around the base of the claw. The bones, 'too, were of great size and strength. The ground-sloth ranged over both North and South America, and it was very common on both continents. The above sketch was taken from that of Hay, Iowa Geo!. Surv., Vol. XXIII, 1914. https://scholarworks.uni.edu/pias/vol33/iss1/39 2 Delavan: Some Recent Finds of Remains of the Extinct Ground Sloth in South
"(fl...., 0H >...., ;:8 M > c MEGALONYX (") z SPECIMEN COLLECTOR LoCALITY I CITATIOX AVTIWR 8 I. Bones and teeth ...... \Vhitney ... Dubuque County ..... Geo!. S. Wis. Vol. I 1862 p. 135 .... Whitney ~ M< ~ ~ i>l Bones and teeth ...... Whitney ... Dubuque County ..... G. S. Ill. Vol. I 1866 p. 162 & 422( ?) Worthen J:Tj H [fl Bones and teeth ...... Whitney ... Dubuque County ..... !Iowa G. S. XXIII 1914 p. 127 ..... Hay n 0 .... 2 J:Tj Claw ...... \odd ...... M!lls County ...... Proc.A.A.A.S. XXXVII 1889, p. 202 Tod~ ::;: ~ . 1 ~ ?> 0 Claw ...... 1odd ..... Mills County ...... Bull. Geo!. S.A. XX 1910p. 353 .... Calvm >--? '"<) Claw ...... Todd ...... Mills County ...... Iowa G. S. XX III 1914 p. 127 ...... Hay H 3. Ungual phalange ...... Shimek .... Plymouth County .... !Iowa G. S. XXIII 1914 p. 128 ...... Hay ::1 ::;:0 4. Patella ...... Unknown .. Plymouth County ... · 1BulL G. S. A. XXII 1911 p. 215 .... Calvin 7: Patella ...... l:nknown .. Plymouth County .... Iowa G. S. XXIII 1914 p. 129 ..... Hay t:J ~ 5. if;. Right radius ...... Unknown .. Monona County ...... 1I3ull. G. S. A. XXIl 1911 p. 215 .... Calvin >--< R!ght i:a?ius ...... ~nki;own .. Mon~na County ..... · jlowa G. S. XXIII 1914 p. 129 ...... Hay. z 6. R~ght t:b:a ...... Calv~n ..... Harr~son County .... · 1Il.ul.l. G. S. ~ .. XXII 191.1 p. 215 .... Calvm Ul Right tibia ...... Odvm ..... Harrison County ....•. Iowa G. S. XXIII 1914 p. 130 ...... Hay 0 7. Lumbar vertebra ...... Shimek .... Harrison County ..... Iowa G. S. XXIII 1914 p. 130 ...... Hay ,. 8. 1st and 2nd phalange of R. hind footi Shimek .... Harrison County ..... ;Bull. G. S. A. XXI 1910 p. 127 .... Shimek .::3 ~ 1st and 2nd phalange of R. hind foot' Shimek .... Harrison County ..... !Iowa G. S. XX III 1914 p. 131...... Hay 5'. 9. ~· ~u~erus ...... R. Leonard. Potta\\
1. Claw ...... ,F. Delavan.I Mills County ...... · 1 2. Tooth, molar ..•...... F. Delavan. Mills County ...... 3. Tooth, molar...... Geo. Day. . . Fremont County .... .
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